Preparation of lithium initiator for the preparation of star polymers

Abstract

Divinyl benzene and/or diisopropenyl benzene in hydrocarbon solvent is added over a period of time at low temperature to a hydrocarbon solvent containing a C 2-20 normal, secondary or tertiary alkyl or cycloalkyl lithium compound and a tertiary alkylamine having 2-4 carbon atoms prepared at low temperature to provide an initiator having an average of from 4 to 9 C-Li sites and a VPO Mn of from about 750 to 4,000. These initiators are useful in polymerizing dienes and vinyl monomers to provide star polymers having an average of from about 4 to 9 arms or branches. These star polymers among other things are useful low profile or low shrink additives for FRPs, e.g., glass fiber reinforced plastics.

We claim: 
     
       1. The method which comprises under an inert atmosphere adding with agitation a tertiary alkyl amine to a RLi compound in a hydrocarbon solvent at a temperature sufficiently low to prevent thermal decomposition of the RLi compound, said tertiary amine having from 2 to 4 carbon atoms in the alkyl group, said R being selected from the group consisting of normal, secondary and tertiary alkyl and cycloalkyl radicals having from 2 to 20 carbon atoms and mixtures thereof, and the mol ratio of said tertiary amine to the RLi compound being about 4:1, and then adding to the resulting mixture with agitation in the same temperature range a diethylenically unsaturated aromatic compound selected from the group consisting of divinyl benzene and diisopropenyl benzene and mixtures thereof in a hydrocarbon solvent, the mole ratio of the RLi compound to the aromatic compound being about 1:0.83, the rate of addition of said aromatic compound to said mixture being sufficient to provide without substantial polymerization a hydrocarbon soluble, gel free and stable initiator suitable for anionic polymerization having an average of from about 4 to 9 C-Li sites and a VPO Mn of from about 750 to 4,000. 
     
     
       2. The method according to claim 1 where said radicals have from 2 to 10 carbon atoms. 
     
     
       3. The method according to claim 1 where said temperature is from about 0° to 25° C. 
     
     
       4. The method according to claim 3 where said radicals have from 2 to 10 carbon atoms. 
     
     
       5. The method according to claim 1 where said temperature is from about 0° to 10° C. 
     
     
       6. The method according to claim 5 where said radicals have from 2 to 10 carbon atoms. 
     
     
       7. The method according to claim 1 where the tertiary amine is triethylamine, the RLi compound is secondary butyllithium and the aromatic compound is divinyl benzene. 
     
     
       8. A hydrocarbon soluble, gel free and stable compound useful as an initiator for anionic polymerization comprising the adduct of RLi where R is selected from the group consisting of normal, secondary and tertiary alkyl and cycloalkyl radicals of from 2 to 20 carbon atoms and mixtures thereof, and a diethylenically unsaturated aromatic compound selected from the group consisting of divinyl benzene and diisopropenyl benzene and mixtures thereof, the mole ratio of RLi to said aromatic compound being about 1:0.83, said adduct having an average of from about 4 to 9 C-Li sites and a VPO Mn of from about 750 to 4,000. 
     
     
       9. A compound according to claim 8 where said radicals have from 2 to 10 carbon atoms. 
     
     
       10. A compound according to claim 8 where RLi is secondary butyl lithium and said aromatic compound is divinyl benzene.